San Bernardino County Sheriff's spokeswoman Cindy Bachman said at a 4 p.m. conference there is a "possiblility (Dorner) could be here somewhere in the forest."

Dorner is suspected of killing one Riverside police officer and critically wounding another early Thursday morning. He is also wanted on suspicion of the Irvine shooting deaths of Cal State Fullerton assistant basketball coach Monica Quan and her fiance, USC public safety officer Keith Lawrence.

Authorities say Dorner is motivated by his desire for revenge after being fired by the Los Angeles Police Department in 2008. Dorner claimed in a manifesto in which he swore violence upon law enforcement officers and his families that he believes he was unjustly fired for reporting another officer needlessly kicked a mentally ill man during a scuffle outside a San Pedro motel.

Investigators found a burning Nissan Titan they believe belonged to Dorner Thursday morning in the parking lot of Bear Mountain Ski Resort. Deputies and police officers have conducted a heavy search of the Bear Valley area since then, although Friday's snowfall has inhibited their work.

Law enforcement officers have been aided by tracking dogs, but snowfall prevented searchers from using helicopters above the mountain's towns and forested areas. Bachman acknowledged the weather has created a level of frustration for the police and deputies in the mountains, but there have been no weather-related injuries.

"Snow really slowing them down," Bachman said.

Friday's efforts led deputies to mountain property owned by Dorner's mother in the San Bernardino Mountains. The area was searched and cleared. Command operations have been headquartered at the San Bernardino County Sheriff's Big Bear station. Deputies will return there at sundown, and 12 two-person units will be on patrol overnight in addition to the area's usual patrols.

Dorner is considered to be armed and dangerous. Los Angeles Police Chief Charlie Beck said Thursday he is believed to be carrying multiple weapons, including assault rifles.

Two deputies assigned to a search told a reporter that if they accept the risk of being killed in the line of duty while working to end Dorner's acts of domestic terrorism.